REDU format ruling
Backfire

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)If a face-up FIRE monster(s) you control is destroyed and sent to the GY: Inflict 500 damage to your opponent.
Rulings
When a FIRE monster(s) on your side of the field is destroyed and sent to the GY, inflict 500 points of damage to your opponent's Life Points.
- If a monster is FIRE because it is equipped with Scroll of Bewitchment, you cannot activate Backfire's effect when it is sent to the GY because it is no longer equipped when it arrives in the GY.
- When multiple FIRE monsters are sent to the GY simultaneously, the damage is only 500 points.
- If you control Backfire and your opponent's FIRE monster, you can activate Backfire's effect when your opponent's monster that you control is destroyed.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.